Along with the development of nano technology, there have been conducted many studies on feeding devices for nano-scale ultra-precise displacement feeds and methods for precisely measuring feeds of the feeding devices. A conventional stage for measuring a feed on the order of nanometers employs a laser interferometer using a laser, or a constant voltage displacement sensor for measuring a displacement using electricity. However, this measurement device is based on the basic precision of a measurement system. That is, measurement of a displacement of 1 nm requires a measurement system with a precision on the order of 1 nm.
Thus, in order to more precisely measure a displacement, the conventional displacement measurement stage requires a more precise measurement system, leading to a problem of increases in the price of the measurement system. In addition, as the measurement system becomes more precise, it is more influenced by ambient environments, resulting in a degraded precision. Thus, in order to keep the precision of the measurement system, stable environments under which the measurement device can operate normally are required. Due to these reasons, environments should be subjected to control that requires a number of systems. Thus, there is a problem in that the measurement system is provided at high costs. Accordingly, there are problems in that the conventional displacement measurement stage can hardly keep its precision due to environmental factors and should be provided with expensive equipment.